1. Field of the Invention
The present invention relates to high frequency antennas and more specifically to antennas for use in finline transmission systems.
2. Description of the Prior Art
Finline apparatus for transmitting high frequency electromagnetic energy is well known in the art. Such apparatus contains two thin coplanar conductive fin elements which are spaced apart along their entire length so that the adjacent edges of the fin elements form a narrow slot capable of supporting the electromagnetic field associated with the energy being transmitted and of confining this energy to a narrow region around the finline element. Various antennas for use with finline transmission components have been developed. In one type of prior art antenna, for example, the slot width of a radiating section of the fin elements is tapered linearly outward for a length approximating the free space wavelength of the microwave energy to be radiated. Another prior art antenna, suitable for suitable transmission systems, is the "Vivaldi" antenna wherein flat coplanar plates are tapered outwardly to form a radiating aperture. The Vivaldi antenna is characterized in the tapered edges follow an exponential rather than a linear curve and provide constant beamwidth over a wide frequency range.
The antenna of the present invention provides relatively uniform performance and low side lobes over a wide frequency range, yet is comparatively easy to fabricate and relatively insensitive to dimensional variations.